1. Field of the Invention
This invention relates to a portable operation device provided for a controller that controls a machine tool or a robot.
2. Description of the Prior Art
Some of controllers for machine tools have a portable operation panel which may be carried by a user. Robot controllers also generally have portable operation sections, such as teaching pendant, which may be carried by the user. Such portable operation sections have a display section using liquid crystal or the like and an input operation section such as various keys and switches and have therein precision circuits.
Conventional portable operation sections have been recognized as a part of a controller or an extension of a controller, so that they have been considered that they may be subjected to no impact from outside, though they are portable, similarly to the case of controllers.
A portable operation section is generally operated by an operator who holds it by the hands. Accordingly, there may be a case where an operator who operates a portable operation section drops it by mistake to give it an impact. However, as the conventional portable device has been designed on the assumption that it will never be subjected to an impact, as described above, it is not equipped with an impact detection device or the like. In consequence, when the conventional portable operation section is dropped by mistake, an operator only visually checks for the appearance thereof and then continues to use it as long as no damage is found from the appearance.
However, when the portable operation section is subjected to an impact by the drop or the like, there may a case where a failure in an internal circuit such as an electric circuit or a mechanism or the like is caused, though the appearance is kept as it is. Such a trouble may not be detected through the check of the appearance, so that a continuous use of the portable operation section having such a trouble would cause an unintended motion by the mechanism section of a machine tool or a robot as an object to be controlled, causing a dangerous situation.